Which of the following acts as both an oxidizing and a reducing agent?

From the given reactions,identify the disproportionation reaction:
$(i) \ Cl_{2(g)} + 2KI_{(aq)} \longrightarrow 2KCl_{(aq)} + I_{2(s)}$
$(ii) \ Cl_{2(g)} + 2OH^{-}_{(aq)} \longrightarrow ClO^{-}_{(aq)} + Cl^{-}_{(aq)} + H_2O_{(l)}$
$(iii) \ Mg_{(s)} + 2HCl_{(aq)} \longrightarrow MgCl_{2(aq)} + H_{2(g)}$
$(iv) \ 2H_2O_{2(aq)} \longrightarrow 2H_2O_{(l)} + O_{2(g)}$

$Cu^{+}$ ion is not stable in aqueous solution,because it shows $-$

Which of the following acts as both an oxidizing and a reducing agent?

Auto-oxidation of bleaching powder gives

The dibasic oxoacid of phosphorus on disproportionation gives two products $A$ and $B$. $A$ and $B$ are respectively